DESCRIPTION

The function _exit() terminates the calling process "immediately". Any
open file descriptors belonging to the process are closed; any children
of the process are inherited by process 1, init, and the process’s
parent is sent a SIGCHLD signal.
The value status is returned to the parent process as the process’s
exit status, and can be collected using one of the wait(2) family of
calls.
The function _Exit() is equivalent to _exit().

RETURNVALUE

These functions do not return.

CONFORMINGTO

SVr4, POSIX.1-2001, 4.3BSD. The function _Exit() was introduced by
C99.

NOTES

For a discussion on the effects of an exit, the transmission of exit
status, zombie processes, signals sent, etc., see exit(3).
The function _exit() is like exit(3), but does not call any functions
registered with atexit(3) or on_exit(3). Whether it flushes standard
I/O buffers and removes temporary files created with tmpfile(3) is
implementation-dependent. On the other hand, _exit() does close open
file descriptors, and this may cause an unknown delay, waiting for
pending output to finish. If the delay is undesired, it may be useful
to call functions like tcflush(3) before calling _exit(). Whether any
pending I/O is canceled, and which pending I/O may be canceled upon
_exit(), is implementation-dependent.